Alarm device



M. T- SLIMAN Oct. 29, 1968 ALARM DEVICE Filed Sept. 5. 1965 Ma mmm N m m m vl A United States Patent Filed Sept. 3, 1965, Ser. No. 484,860 2 Claims. (Cl. 340280) ABSTRACT OF THE DISCLOSURE Means disposed within an encased electrical appliance for energizing a remotely positioned alarm device upon attempted unauthorized removal of the appliance from a given location and including a source of electrical energy common to the appliance and to the alarm device; means in the casing for generating a first voltage, means at the remotely located alarm device for generating a second voltage, aseries circuit including an alarm indicator means and a unidirectional current passing device connected between said voltage generating means, the current passing device becoming operative, and consequently the indicator means, when the potential on the current passing device becomes less than the second voltage but is greater than the second voltage minus the first voltage, and interlocking current carrying means on the casing and connecting the electrical appliance and the first voltage generating means in the casing with said common source of electrical energy.

This invention relates to an alarm device associated with a television set, coin vending machine, radio, or other electrical appliance for signaling that the appliance is being tampered with by unauthorized persons and is an improvement over my copending application Ser. No. 472,888, filed July 19, 1965.

There is disclosed in the aforementioned application a power take-off plate positioned externally of an electrical appliance surrounding the interlock on the back wall thereof drawing electrical current through the power line leading to the appliance. A relay positioned within the appliance is connected to an alarm circuit for sounding the alarm when the connection between the interlock, power take-off plate and appliance power cord is disturbed.

'It has been found that a wary person knowledgeable of alarm devices may avoid the alarm system of the aforementioned application by removing the back wall -of the appliance without disturbing the interlock mechanism.

It is an object of the instant invention to provide an alarm device for securement to an electrical appliance such that tampering with the appliance in any manner will activate a remotely positioned alarm.

Another object of the instant invention is to provide an alarm device for electrical appliances having the major components thereof housed within the appliance.

Still another object of the instant invention is to provide an alarm device which may be installed within pre exisitng electrical appliances or which may be installed concurrently with the assembly of the appliance.

A more specific object of the instant invention is to provide a power take-off connection interiorly of the appliance from the power source leading to the appliance such that the removal of the rear wall thereof will actuate an alarm system.

Other objects and advantages of the instant invention reside in the combinations of elements, arrangements of parts, and features of construction and operation, all as will be more fully pointed out hereinafter and disclosed in the accompanying drawing wherein there is shown a preferred embodiment of this inventive concept.

In the drawing:

FIGURE 1V is a side elevational view of an electrical 3,408,643 Patented Oct. 29, 1968 appliance, illustrated as a television set, positioned in a room and equipped with an alarm device of the instant invention;

FIGURE 2 is a schematic view of the alarm circuit of the instant invention; and

. FIGURE 3 is a front elevational view of a power takeoff plate of the instant invention, certain parts being broken away for clarity of illustrations. 1

Referring now to the drawing in detail, wherein lik reference characters designate like elements throughout the several views thereof, there is indicated generally at 16 an electrical appliance which is illustrated as a television set, but which may be a radio, a vending machine such as a candy or cigarette dispenser, or any other electrical appliance which is susceptible of being stolen, positioned on a floor 12 adjacent a wall 14 of a room generally indicated at 16. Television set 10 is supported from floor 12 by a plurality of customary legs 18 and is provided with side walls 20, a front wall 22, a rear wall 24, and a top wall 26 to form the customary appliance case.

The electrical power for operating electrical appliance 10 is drawn from a conventional electric outlet 28, including a face plate 30 having the conventional female outlets 32 to which are connected a pair of alternating current power lines 34 in a conventional manner.

Connecting electrical outlet 28 to television set 10 is a conventional power cord designated generally at 36 having a male plug 38 providing male prongs 40. Power cord 36 includes a pair of wires 42 connected to prongs leading to an interlock shown generally at 44 positioned on back wall 24 of appliance 10. Power cord 36 includes a female plug 46, which also comprises a part of interlock 44, receiving a pair of male prongs 48 extending from a resilient plug 50 secured in rear wall 24. Resilient plug 50 includes a pair of male prongs 52 extending interiorly of the case of appliance 10 with a pair of wires 54 shown schematically in FIGURE 2 leading to the electrical components operating appliance 10.

The alarm circuit of, the instant invention is indicated generally at 56 in FIGURE 2 and includes a first transformer shown generally at 58 positioned within appliance 10 including a primary winding 60 and a secondary winding 62. Primary winding 60 is connected to the source of electrical power feeding through interlock 44 by a power take-off plate shown generally at 64. Power take-off plate 64 includes a dielectric body 66 housing a pair of spaced apart parallel metallic grommets 68 forming a pair of openings 70 receiving male prongs 52 of interlock 44. Each of grommets 68 is electrically connected to a wire 72 secured to primary winding 60. It will be appreciated that electrical current will flow from electrical outlet 28 through interlock 44 and wires 72 to energize primary winding 60 in a known manner.

One connection of secondary winding 62 is connected to an electrical wire 74 leading to a ground 76 which is preferably a ground of the electrical components of appliance 10. The other connection of secondary winding 62 is secured to an electrical conduit 78 leading exteriorly of appliance 10 and connected to an alarm call board circuit indicated generally at 80 positioned at a remote location. The electrical configuration of first transformer 58 is preferably such that primary winding 60 will accom-- modate the nominal volt potential with secondary winding 62 creating a voltage across wires 74, 78 on the order of 25 volts.

Alarm call board 80 is preferably located at a guard station, such as in the ofiice of a motel or hotel in which a plurality of appliances 10 are located. Alarm call board 80 preferably includes a diode 82 connected to wire 73 such that diode 82 normally passes current from right to left as indicated in FIGURE 2. The other connection of diode 82 is connected by a wire 84 to a signaling device 86, which is illustrated as a lamp, but which may be of any desired type. An outlet wire 88 leads from signaling device 86 to a secondary coil 90 of a second transformer shown generally at 92. Transformer 92 includes a primary coil 94 energized through a pair of electrical conduits 96 provided with a male plug 98 having male prongs 100. Prongs 100 are inserted into a female outlet connection 102 of an electrical outlet shown generally at 104.

The electrical configuration of second transformer 92 is such that primary coil 94 will accommodate a nominal 110 volt potential with secondary coil 90 creating a potential on the order of 70 volts. As more fully explained hereinafter, female outlets 28, 104 and the grounds for secondary coils 62, 90 of transformers 58, 92 are arranged such that first transformer 58 creates a potential tending to induce flow shown by an arrow 106 in FIGURE 2. Second transformer 92 is arranged to create a voltage potential tending to induce electrical flow as shown by an arrow 108 in FIGURE 2 in a direction opposite with respect to arrow 106.

Diode 82 is preferably of the type that freely passes current in the direction of arrow 106 and precludes electrical flow in the direction of arrow 108 until a'predete'rmined potential is created across the connections of diode 82. For purposes of convenience, the voltage potential created by secondary coil 62 of first transformer 58 is termed V while the voltage potential induced by secondary coil 90 of second transformer 92 is termed V Diode 82 is selected such that the aforementioned predetermined potential which enables diode 82 to pass current in the direction of arrow 108 is less than V but is greater than V minus V i It shouldnow be apparent that when alarm circuit 56 is completed, little if any current flow will be conducted by diode 82 since the unidirectional transmission characteristics thereof preclude electrical flow in the direction of arrow 108 while the higher potential created by coil 90 precludes electrical flow in the direction of arrow 106. If an individual tampers with electrical appliance and attempts to remove it from room 16, the intruder must do one of several things to break the electrical connection between the electrical components of appliance 10 and female outlet 28. The prospective thief may remove male plug 38 from female outlet 28, sever electrical power cord 36, remove female plug 46 from interlock 44, or remove rear wall 24 from appliance 10.

Any of these manipulations will deenergize first transformer 58 with the potential in wire 78 falling to zero because of ground 76. When the potential in wire 78 falls to a point such that the potential in wire 84 exceeds the unidirectional capability of diode 82, secondary coil 90 of second transformer 92 will generate sufficient potential to move electrical current through signaling means 86, wire 84, diode 82 and wire 78 in sufficient quantities to activate signaling means 86 thus indicating to an individual adjacent alarm call board 80 that appliance 10 is being tampered with. p

In the event that the prospective thief attempts to avoid alarm circuit 56 by severing wire 78, the potential thereof will fall to zero because wire 78 will inevitably become grounded thus allowing current flow through diode 82 in the direction of arrow 108 sounding alarm means 86 as previously indicated. It should be understood that a plurality .of signaling means may be provided at alarm call board 80 to accommodate a multiplicity of electrical appliances 10.

As previously indicated, female outlets 28, 104 in the grounds of secondary coils 62, 90 are polarized to ensure current flow in the desired directions. Although this polarization may be effected in any desired manner, one means of doing so is illustrated in FIGURE 2 where a common wire 110 of the hotel or motel is grounded as .4 at 112 and connected by a wire 114% seao'riaa'r 'edn '90 and by a wire 116 to secondary coil 62. One of wires 34 leading from female outlet 28 is likewise secured to common wire 110 while anelectrical conduit 118 connects common wire 110 with female outlet 104 serving alarm call board circuit ,80. The other of wires 3.4 leading from female outlet 28 is connected to a common hot wire 120 which is connected by wire'122 to female outlet 104.

It is now seen that'there is herein :provided an improved alarm device havingall of the objects of this invention, and others, including many advantages of great practical utility and commercial importance.

Since many embodiments may be made of'the instant inventive concept, and since many modifications may be made of the embodiment hereinbefore shownand described, it is to be understood that the foregoing is to be interpreted merely as illustrative and not in a limiting sense.

Iclaim: i

1. An alarm device comprising in combination an electrical appliance having an enclosed case including a removably mounted rear wall carrying an electric interlockproviding electrical access to the interior of said appliance and for connection to said appliance to supply the operating voltage therefor, an electrical power source connected with said electric interlock and including a hot connection within said case in electrical communication with said interlock, electrical power take-off means positioned interiorly of said case in communication with said hot connection, first transformer means positioned within said case and having a first primary winding connected to said power take-oh means and a first secondary winding generating a first voltage having a side thereof connected to a wire leading exteriorly of said case, the other side of said second secondary Winding being grounded to the ground of the appliance and to the ground of the power source, a remotely positioned alarm signal board including second transformer means having a second primary winding for connection to said power source, and a second secondary winding generating a second voltage not less than said first voltage, means connecting one side of said second secondary winding to the ground of said power source, means connecting the other side of said second secondary winding of said second transformer to said exterior wire including in a series circuit a signaling means anda diode having a unidirectional current flow characteristic for passing current from said first transformer toward said second transformer and blocking current fiowfrom said second transformer toward said first transformeruntil a third predetermined voltage exists across said diode under which condition current passes toward saidfirst transformer, said third predetermined voltage being less than said second prede= termined voltage and greater than the remainder of said second predetermined voltage minus said first predetermined voltage, whereby de-energization of said first transformer means results in current passing from said second transformer means toward said first transformer means. 2. The structure of claim 1 wherein said power take-01f means includes a dielectric plate housing metallic grommets and electrical connections leading from said grommets to said first coil of said first transformer means, said electric interlock includes a pair of prongs extending interiorly of said casing, said grommets receiving said prongs.

References Cited UNITED STATES PATENTS JOHN W. CALDWELL, Primary'Examiner.

D. L. TRAFTON, Assistant Examiner. 

